Wireless communication device and associated method including control of positioning-system receiver and shared oscillator

ABSTRACT

The wireless communication device includes a wireless communication transceiver to generate an oscillator control signal and an activation signal, a positioning-system receiver (e.g. a GPS receiver) to process received positioning signals, and a shared oscillator (e.g. a temperature compensated and voltage controlled crystal oscillator TCVCXO) responsive to the oscillator control signal and to generate a reference frequency signal for the wireless communication transceiver and the positioning-system receiver. The positioning-system receiver may control processing of the received positioning signals based upon the activation signal to reduce a noise contribution (e.g. phase noise) due to frequency control of the shared oscillator based upon the oscillator control signal. The activation signal may indicate that the oscillator control signal is being varied to provide frequency control or adjustment of the shared oscillator.

RELATED APPLICATION

This application is a continuation of pending Ser. No. 12/468,152 filedMay 19, 2009, which, in turn, is a continuation of Ser. No. 11/695,111filed Apr. 2, 2007 now U.S. Pat. No. 7,551,131 issued Jun. 23, 2009,which claims the benefit of U.S. Provisional Application No. 60/789,813filed Apr. 6, 2006, the entire disclosures of which are incorporatedherein by reference in their entireties.

FIELD OF TECHNOLOGY

The present invention relates to the field of communications, and, moreparticularly, to handheld wireless communications, locationdetermination and related methods.

BACKGROUND

A Global Positioning System (GPS) receiver may be implemented in ahandheld wireless communication device, such as a cellular phone. Forexample, United States Patent Application 2006/0250302 to Park et al.entitled “Apparatus and method for receiving GPS signals in a mobileterminal” is directed to an apparatus and method for increasing GPSreception sensitivity in a mobile terminal having a mobile-based GPSpositioning function. A GPS receiver in the mobile terminal receivessensitivity assistance (SA) data by using basic information about GPSsatellites and system time. The GPS receiver then correlates a PRN codewith a GPS signal and coherent-integration of the correlation result byusing the SA data. It calculates a position of the mobile terminal byusing the integrated samples.

In the Enhanced 911 (E911) program, the GPS should be able to determinethe location of the cellular phone even when a user makes emergencycalls in an indoor environment, where the GPS receiver does not haveview of the sky. High sensitivity is required for such an application,such as −155 dBm or higher.

United States Patent Application 2004/0102165 to Bloebaum et al.entitled “Compensation for frequency adjustment in mobilecommunication-positioning device with shared oscillator” discloses amethod for compensating for a frequency adjustment in an oscillatorshared between a communication circuit and a positioning signalreceiver. In one embodiment, the method begins to receive and store apositioning signal at a first time point. When, at a second time point,the operating frequency of the shared oscillator is adjusted, thefrequency adjustment is recorded. After the positioning signal iscompletely received and stored, the processing of the positioning signaltakes into consideration the frequency adjustment. In that embodiment,the processing hypothesizes a frequency shift in the receivedpositioning signal. In another embodiment, the method for determiningthe operating frequency of the oscillator detects a beginning time pointof a reference signal received by the mobile communication device andenables a counter to count in step with a clock signal derived from theoscillator. When an ending time point of the reference signal isreceived by the mobile communication device, the count is stopped, andthe frequency of the oscillator is determined based on the count in thecounter and an expected time that elapsed between the beginning timepoint and the ending time point.

Achieving high sensitivity, a GPS receiver will try to correlate thelocal pseudo noise (PM) with the received signal using longest possiblecoherent correlation length. Coherent correlation length is limited bythe phase noise of the frequency and time reference of the GPS receiver,which is usually implemented as a TCVCXO (temperature compensated andvoltage controlled crystal oscillator). A low phase noise GPS TCVCXO maybe critical to sensitivity performance.

The cellular transceiver usually also has a TCVCXO, that is controlledby an AFC (automatic frequency control) loop. The loop continuallyadjusts the control voltage of the cellular TCVCXO to maintain lowfrequency error that meets requirements of the cellular transceiver.

When the GPS receiver and the cellular transceiver share a singleTCVCXO, the conventional AFC loop will usually make the phase noise ofthe TCVCXO too high for use of the GPS receiver, causing loss of GPSsensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a wireless communicationdevice in accordance with an example of an embodiment of the presentinvention.

FIG. 2 is a schematic block diagram illustrating various details of anexample of an embodiment of the wireless communication device of FIG. 1.

FIG. 3 is a schematic block diagram illustrating exemplary components ofa mobile wireless communications device in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In view of the foregoing background, it is therefore an object of thepresent invention to provide an approach to reduce and/or eliminate thephase noise contribution in the control of the positioning-systemreceiver due to frequency adjustment of the shared oscillator.

This and other objects, features, and advantages in accordance with thepresent embodiments are provided by a wireless communication deviceincluding a wireless communication transceiver to generate an oscillatorcontrol signal and an activation signal, a positioning-system receiver(e.g. a GPS receiver) to process received positioning signals, and ashared oscillator (e.g. a temperature compensated and voltage controlledcrystal oscillator TCVCXO) responsive to the oscillator control signaland to generate a reference frequency signal for the wirelesscommunication transceiver and the positioning-system receiver. Thepositioning-system receiver may control processing of the receivedpositioning signals based upon the activation signal to reduce a noisecontribution (e.g. phase noise) due to frequency control of the sharedoscillator based upon the oscillator control signal. The activationsignal may indicate that the oscillator control signal is being variedto provide frequency control or adjustment of the shared oscillator.

The wireless communication transceiver may include an automaticfrequency control (AFC) module to generate the oscillator control signaland the activation signal. Also, a first frequency synthesizer mayprovide clock signals to the AFC module based upon the referencefrequency signal. The positioning-system receiver may include a secondfrequency synthesizer to provide clock signals for thepositioning-system receiver based upon the reference frequency signal. Acontroller may control processing of the received positioning signalsbased upon the activation signal from the AFC module.

The positioning-system receiver may further include a coherentcorrelator to correlate locally generated pseudo noise with the receivedpositioning signals, a non-coherent combiner to non-coherently combinecorrelation results from the coherent correlator, and a pseudo-rangecalculator to calculate pseudo-ranges based upon non-coherently combinedcorrelation results from the non-coherent combiner. The controller mayprovide control signals to the coherent correlator and the non-coherentcombiner based upon the activation signal from the AFC module.

The wireless communication transceiver may include a first downconverter to down convert received communication signals, an automaticfrequency control (AFC) module connected downstream from the downconverter and generating the oscillator control signal and theactivation signal, a digital-to-analog converter (DAC) receiving theoscillator control signal from the AFC module, and a first frequencysynthesizer to provide clock signals to at least the first downconverter and AFC module based upon the reference frequency signal.Also, the positioning-system receiver may include a second downconverter to down convert received positioning signals, a coherentcorrelator downstream from the second down converter to correlatelocally generated pseudo noise with the received positioning signals, anon-coherent combiner to non-coherently combine correlation results fromthe coherent correlator, a pseudo-range calculator to calculatepseudo-ranges based upon non-coherently combined correlation resultsfrom the non-coherent combiner, a second frequency synthesizer toprovide clock signals to at least the second down converter based uponthe reference frequency signal, and a controller to provide controlsignals to the coherent correlator and the non-coherent combiner basedupon the activation signal from the AFC module.

A method aspect is directed to operating a wireless communication deviceincluding generating an oscillator control signal and an activationsignal with a wireless communication transceiver, processing receivedpositioning signals with a positioning-system receiver, and generating areference frequency signal for the wireless communication transceiverand the positioning-system receiver with a shared oscillator responsiveto the oscillator control signal. The method includes controllingprocessing of the received positioning signals at the positioning-systemreceiver based upon the activation signal to reduce a noise contributiondue to frequency control of the shared oscillator.

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

The present method and apparatus is for controlling a positioning-system(e.g. GPS) receiver and a shared oscillator (e.g. TCVCXO) shared by theGPS receiver and a cellular transceiver to effectively relax the phasenoise requirement without significant loss of GPS sensitivity, and stillmeeting the frequency accuracy requirements of the cellular network.

Referring initially to FIGS. 1 and 2, a mobile wireless communicationsdevice 20 and associated method of operating in accordance with thepresent invention will now be described. The device 20 illustrativelyincludes a portable housing 21 and one or more wireless transceivers 22(e.g. a cellular transceiver) carried by the portable housing. In theexample illustrated in FIG. 1, a cellular transceiver 22 cooperates witha cellular antenna 23 to communicate over a cellular network 24 via abase station(s) 25, which is shown as a cell tower for clarity ofillustration. In other embodiments, the wireless transceiver 22 be awireless local or personal area network (LAN/PAN) transceiver forcommunicating via a wireless LAN/PAN, for example. In still furtherembodiments, both cellular and wireless LAN/PAN transceivers may beincluded, as will be appreciated by those skilled in the art.

The device 20 further illustratively includes a satellite positioningsignal receiver 26 carried by the portable housing 21. By way ofexample, the satellite positioning signal receiver 26 may be a GPSreceiver, although receivers compatible with other satellite positioningsystems such as Galileo, for example, may also be used. An antenna 27 isalso carried by the portable housing 21 and is connected to thesatellite positioning signal receiver 26 for receiving positioningsignals from GPS satellites 28, as will be appreciated by those skilledin the art. It should be noted that in some embodiments the antenna 27may also be connected to the wireless transceiver(s) 22 and used forcommunicating over a wireless network(s) as well, as will be appreciatedby those skilled in the art.

A shared oscillator 29 provides reference signals to each of thewireless communications transceiver 23 and the positioning-systemreceiver 26 as will be appreciated by those skilled in the art.

Referring more specifically to an example of an embodiment asillustrated in FIG. 2, the simplified block diagram does not attempt toshow all components but only selected components that are closelyrelated to the invention. Those skilled in the art can recognize thatthe transmitter is omitted, for example; and in the receiver, not allcomponents are shown, such as amplifiers, filters, A/D converter, etc.In the cellular transceiver and modem 22, there is a down converter thatconverts the received signal from antenna 23 to lower frequencies(intermediate frequency (IF) and/or baseband). An AFC control processingmodule 32 compares the received signal frequency with a locallygenerated frequency and produces a control or adjustment signal to besent to DAC (digital to analog converter) 34, the analog version of thecontrol signal is smoothed by a LPF 44 (low pass filter) to control thefrequency of the TCVCXO 42 of the shared oscillator 29.

The local oscillator frequency provided to the down converter 30, theAFC control module 32 and other clock frequencies (such as samplingfrequency, not shown) may be generated by frequency synthesizer module36 that may typically include PLLs (phase locked loop) based on thereference frequency signal produced by the TCVCXO 42. The control signal(output of LPF 44) is provided into the TCVCXO 42 from time to time totrim the oscillating frequency of the TCVCXO to maintain the desiredfrequency accuracy. Since the frequency is continually adjusted, theadjustments effectively add additional phase noise to the TCVCXO, andunder certain conditions, it may be the dominating contributor to thephase noise of the TCVCXO.

The GPS receiver 26 receives GPS signals from GPS antenna 27. The GPSreceiver 26 also has a down converter 50 that translates the receivedsignal to a lower frequency, IF and/or baseband. The down converter 50makes use of a local oscillator signal obtained from a frequencysynthesizer 60 to accomplish the frequency translation. The frequencysynthesizer 60 also produces other clock signals distributed to othervarious components in the GPS receiver 26. The frequency synthesizer 60is based on the reference frequency signal produced by the TCVCXO 42 toproduce the needed frequency signals.

The phase noise, including that contributed by the AFC loop on thecellular transceiver and modem 22, will be translated to the outputsignals, that may degrade GPS receiver sensitivity. In the GPS receiver26, there may be a coherent correlator 52, receiving signals from downconverter 50 (details such as amplifiers, filters, A/D are omitted forease of explanation) that correlates a locally generated PN (pseudonoise) with the received GPS signals at various hypothesis time delayson a given frequency bin (or referred to as Doppler bin). Within thelength of the correlation, the correlation results are “voltage-added”,i.e., coherently combined. If there exists phase noise in the downconversion processing, the results may or may not add up constructively,depending on the phase of the down-converted signal at the time instantsthat is affected by the phase noise of the TCVCXO.

The coherent correlation results are then further non-coherentlycombined at a non-coherent combiner 54, and the pseudo-range iscalculated by the pseudo range calculator 56. Non-coherent combining isa combination operation that does not involve the phase of the signals,such as combining in power, in energy or in magnitude, etc.

In addition to how a conventional AFC control operates, the AFC controlmodule 32 further produces an activation signal 62 that signals thecontroller 58 for the GPS receiver. The signal 62 is activated beforethe AFC control module 32 varies its TCVCXO control output value, anddeactivated after the AFC control module 32 finishes updating the itsTCVCXO control output value, and the frequency of the TCVCXO 42 settles.During the period the signal 62 is deactivated, the AFC control module32 holds a constant value for the TCVCXO control signal. In other words,the phase noise contribution caused by AFC adjustment only exists whensignal 62 is activated and does not exist when signal 62 is deactivated.

The controller 58 further controls the coherent correlator 52 such that,in a high sensitivity mode of the GPS receiver operation, the coherentcorrelation begins and ends only during the period while the signal 62is deactivated and preferably does not cross over any portion of theactivated period of signal 62. The controller 58 also controls thenon-coherent combiner 54 such that the correlation results obtainedbefore an activation period of signal 62 and after the deactivation ofthe signal 62 following the activation period will be combined onlynon-coherently, if any combining will happen, in a high sensitivity modeof the GPS receiver operation. During activation of signal 62, it ispreferred that no correlation of the signal is performed or its resultsare used for calculation of pseudo-range calculations for highsensitivity mode of operation.

It may be further desirable to estimate the down-converted GPS signalfrequency difference before and after the AFC adjustment, so that thecorrelation results before and after the adjustment are combined withthe appropriate frequency bins according to the frequency change made bythe AFC adjustment. Note that in low sensitivity mode of operation, theabove restrictions may not have to be applied, because performance oflow sensitivity operation mode may not be significantly affected by thephase noise contribution of AFC adjustment.

The signal 62 may be further combined with one or a plurality of signalsthat indicate the activation of wireless transmitters (such as acellular transmitter, a WLAN transmitter, etc., residing in the wirelesshandheld device, not shown in drawing) and the combined signal may beused to accomplish the above control tasks on the GPS receiveroperation. When the signals are active HIGH, the combining of the two(or more) signals may be logically OR-ed, for example.

Accordingly, the GPS receiver 26 may control processing of the receivedpositioning signals based upon the activation signal 62 to reduce anoise contribution (e.g. phase noise) due to frequency control of theshared oscillator 29 based upon the oscillator control signal. As such,the activation signal 62 may indicate that the oscillator control signalis being varied to provide frequency control or adjustment of the sharedoscillator 29.

A method aspect is directed to operating the wireless communicationdevice 20 including generating an oscillator control signal and anactivation signal with a wireless communication transceiver 22,processing received positioning signals with a positioning-systemreceiver 26, and generating a reference frequency signal for thewireless communication transceiver and the positioning-system receiverwith a shared oscillator 29 responsive to the oscillator control signal.The method includes controlling processing of the received positioningsignals at the positioning-system receiver 26 based upon the activationsignal to reduce a noise contribution due to frequency control of theshared oscillator 29.

In the method, generating the oscillator control signal and theactivation signal may include generating the oscillator control signaland the activation signal with an automatic frequency control (AFC)module 32 of the wireless communication transceiver 22, and may furtherinclude providing clock signals to the AFC module from the firstfrequency synthesizer 36 of the wireless communication transceiver basedupon the reference frequency signal. Also, processing receivedpositioning signals with the positioning-system receiver 26 may includeproviding clock signals from a second frequency synthesizer 60 for thepositioning-system receiver based upon the reference frequency signal,and controlling processing of the received positioning signals with acontroller 58 of the positioning-system receiver based upon theactivation signal from the AFC module 32.

Processing received positioning signals with the positioning-systemreceiver 26 may further include correlating locally generated pseudonoise with the received positioning signals via a coherent correlator52, non-coherently combining correlation results from the coherentcorrelator via a non-coherent combiner 54 and calculating pseudo-rangeswith a pseudo-range calculator 56 based upon non-coherently combinedcorrelation results from the non-coherent combiner. Control signals maybe provided to the coherent correlator 52 and the non-coherent combiner54 from the controller 58 based upon the activation signal from the AFCmodule 32.

Accordingly, the present method and apparatus provides for the controlof the positioning-system (e.g. GPS) receiver 26 and the sharedoscillator 29 (e.g. TCVCXO) shared by the GPS receiver and a cellulartransceiver 22 to effectively relax the phase noise requirement withoutsignificant loss of GPS sensitivity, while still meeting the frequencyaccuracy requirements of the cellular network.

One example of a hand-held mobile wireless communications device 1000that may be used is further described in the example below withreference to FIG. 3. The device 1000 illustratively includes a housing1200, a keypad 1400 and an output device 1600. The output device shownis a display 1600, which is preferably a full graphic LCD. Other typesof output devices may alternatively be utilized. A processing device1800 is contained within the housing 1200 and is coupled between thekeypad 1400 and the display 1600. The processing device 1800 controlsthe operation of the display 1600, as well as the overall operation ofthe mobile device 1000, in response to actuation of keys on the keypad1400 by the user.

The housing 1200 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 1800, other parts of the mobiledevice 1000 are shown schematically in FIG. 3. These include acommunications subsystem 1001; a short-range communications subsystem1020; the keypad 1400 and the display 1600, along with otherinput/output devices 1060, 1080, 1100 and 1120; as well as memorydevices 1160, 1180 and various other device subsystems 1201. The mobiledevice 1000 is preferably a two-way RF communications device havingvoice and data communications capabilities. In addition, the mobiledevice 1000 preferably has the capability to communicate with othercomputer systems via the Internet.

Operating system software executed by the processing device 1800 ispreferably stored in a persistent store, such as the flash memory 1160,but may be stored in other types of memory devices, such as a read onlymemory (ROM) or similar storage element. In addition, system software,specific device applications, or parts thereof, may be temporarilyloaded into a volatile store, such as the random access memory (RAM)1180. Communications signals received by the mobile device may also bestored in the RAM 1180.

The processing device 1800, in addition to its operating systemfunctions, enables execution of software applications 1300A-1300N on thedevice 1000. A predetermined set of applications that control basicdevice operations, such as data and voice communications 1300A and1300B, may be installed on the device 1000 during manufacture. Inaddition, a personal information manager (PIM) application may beinstalled during manufacture. The PIM is preferably capable oforganizing and managing data items, such as e-mail, calendar events,voice mails, appointments, and task items. The PIM application is alsopreferably capable of sending and receiving data items via a wirelessnetwork 1401. Preferably, the PIM data items are seamlessly integrated,synchronized and updated via the wireless network 1401 with the deviceuser's corresponding data items stored or associated with a hostcomputer system. Communication functions, including data and voicecommunications, are performed through the communications subsystem 1001,and possibly through the short-range communications subsystem. Thecommunications subsystem 1001 includes a receiver 1500, a transmitter1520, and one or more antennas 1540 and 1560. In addition, thecommunications subsystem 1001 also includes a processing module, such asa digital signal processor (DSP) 1580, and local oscillators (LOs) 1601.The specific design and implementation of the communications subsystem1001 is dependent upon the communications network in which the mobiledevice 1000 is intended to operate. For example, a mobile device 1000may include a communications subsystem 1001 designed to operate with theMobitex™, Data TAC™ or General Packet Radio Service (GPRS) mobile datacommunications networks, and also designed to operate with any of avariety of voice communications networks, such as AMPS, TDMA, CDMA, PUS,GSM, etc. Other types of data and voice networks, both separate andintegrated, may also be utilized with the mobile device 1000.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore requires a subscriber identitymodule, commonly referred to as a SIM card, in order to operate on aGPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 1000 may send and receive communicationssignals over the communication network 1401. Signals received from thecommunications network 1401 by the antenna 1540 are routed to thereceiver 1500, which provides for signal amplification, frequency downconversion, filtering, channel selection, etc., and may also provideanalog to digital conversion. Analog-to-digital conversion of thereceived signal allows the DSP 1580 to perform more complexcommunications functions, such as demodulation and decoding. In asimilar manner, signals to be transmitted to the network 1401 areprocessed (e.g. modulated and encoded) by the DSP 1580 and are thenprovided to the transmitter 1520 for digital to analog conversion,frequency up conversion, filtering, amplification and transmission tothe communication network 1401 (or networks) via the antenna 1560.

In addition to processing communications signals, the DSP 1580 providesfor control of the receiver 1500 and the transmitter 1520. For example,gains applied to communications signals in the receiver 1500 andtransmitter 1520 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 1580.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 1001and is input to the processing device 1800. The received signal is thenfurther processed by the processing device 1800 for an output to thedisplay 1600, or alternatively to some other auxiliary I/O device 1060.A device user may also compose data items, such as e-mail messages,using the keypad 1400 and/or some other auxiliary I/O device 1060, suchas a touchpad, a rocker switch, a thumb-wheel, or some other type ofinput device. The composed data items may then be transmitted over thecommunications network 1401 via the communications subsystem 1001.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 1100, and signals fortransmission are generated by a microphone 1120. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 1000. In addition, the display 1600may also be utilized in voice communications mode, for example todisplay the identity of a calling party, the duration of a voice call,or other voice call related information.

The short-range communications subsystem enables communication betweenthe mobile device 1000 and other proximate systems or devices, whichneed not necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, or a Bluetooth™ communications module toprovide for communication with similarly-enabled systems and devices.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

That which is claimed is:
 1. A mobile wireless communication devicecomprising: a portable housing: a cellular transceiver carried by theportable housing and comprising an automatic frequency control (AFC)circuit configured to generate an oscillator control signal and anactivation signal; a global positioning system (GPS) receiver carried bythe portable housing; and a shared oscillator carried by the portablehousing and configured to generate a reference frequency signal for thecellular transceiver and the GPS receiver; the GPS receiver configuredto control processing of received positioning signals based upon theactivation signal from the cellular transceiver to reduce the noisecontribution on the reference frequency signal due to frequency controlof the shared oscillator based upon the oscillator control signalincluding controlling coherent correlation of the received positioningsignals in a high sensitivity operation mode based upon the activationsignal.
 2. The mobile wireless communication device of claim 1 whereinthe cellular transceiver includes: a first frequency synthesizerconfigured to provide clock signals to the AFC circuit based upon thereference frequency signal.
 3. The mobile wireless communication deviceof claim 2 wherein the GPS receiver includes: a second frequencysynthesizer configured to provide clock signals for the GPS receiverbased upon the reference frequency signal; and a controller configuredto control processing of the received positioning signals based upon theactivation signal from the AFC circuit.
 4. The mobile wirelesscommunication device of claim 3 wherein the GPS receiver furtherincludes: a coherent correlator configured to correlate locallygenerated pseudo noise with the received positioning signals; anon-coherent combiner configured to non-coherently combine correlationresults from the coherent correlator; and a pseudo-range calculatorconfigured to calculate pseudo-ranges based upon non-coherently combinedcorrelation results from the non-coherent combiner; the controllerconfigured to provide control signals to the coherent correlator and thenon-coherent combiner based upon the activation signal from the AFCcircuit.
 5. The mobile wireless communication device of claim 1 whereinthe cellular transceiver includes: a first down converter configured todown convert received communication signals; a digital-to-analogconverter (DAC) receiving the oscillator control signal from the AFCcircuit; and a first frequency synthesizer configured to provide clocksignals to at least the first down converter and AFC circuit based uponthe reference frequency signal.
 6. The mobile wireless communicationdevice of claim 5 wherein the GPS receiver includes: a second downconverter configured to down convert received positioning signals; acoherent correlator downstream from the second down converter configuredto correlate locally generated pseudo noise with the receivedpositioning signals; a non-coherent combiner configured tonon-coherently combine correlation results from the coherent correlator;a pseudo-range calculator configured to calculate pseudo-ranges basedupon non-coherently combined correlation results from the non-coherentcombiner; a second frequency synthesizer configured to provide clocksignals to at least the second down converter based upon the referencefrequency signal; and a controller configured to provide control signalsto the coherent correlator and the non-coherent combiner based upon theactivation signal from the AFC circuit.
 7. The mobile wirelesscommunication device of claim 1 wherein the activation signal indicatesthat the oscillator control signal is being varied to provide frequencycontrol of the shared oscillator.
 8. The mobile wireless communicationdevice of claim 1 wherein the shared oscillator comprises a temperaturecompensated and voltage controlled crystal oscillator (TCVCXO).
 9. Amobile wireless communication device comprising: a portable housing: acellular transceiver carried by the portable housing and comprising anautomatic frequency control (AFC) circuit configured to generate anoscillator control signal and an activation signal; a global positioningsystem (GPS) receiver carried by the portable housing; and a sharedoscillator carried by the portable housing and configured to generate areference frequency signal for the cellular transceiver and the GPSreceiver; the GPS receiver configured to control processing of thereceived positioning signals based upon the activation signal from thecellular transceiver including controlling coherent correlation of thereceived positioning signals in a high sensitivity operation mode basedupon the activation signal.
 10. The mobile wireless communication deviceof claim 9 wherein the cellular transceiver includes: a first frequencysynthesizer configured to provide clock signals to the AFC circuit basedupon the reference frequency signal.
 11. The mobile wirelesscommunication device of claim 10 wherein the GPS receiver includes: asecond frequency synthesizer configured to provide clock signals for theGPS receiver based upon the reference frequency signal; and a controllerconfigured to control processing of the received positioning signalsbased upon the activation signal from the AFC circuit.
 12. The mobilewireless communication device of claim 11 wherein the GPS receiverfurther includes: a coherent correlator configured to correlate locallygenerated pseudo noise with the received positioning signals; anon-coherent combiner configured to non-coherently combine correlationresults from the coherent correlator; and a pseudo-range calculatorconfigured to calculate pseudo-ranges based upon non-coherently combinedcorrelation results from the non-coherent combiner; the controllerconfigured to provide control signals to the coherent correlator and thenon-coherent combiner based upon the activation signal from the AFCcircuit.
 13. The mobile wireless communication device of claim 9 whereinthe cellular transceiver includes: a first down converter configured todown convert received communication signals; a digital-to-analogconverter (DAC) receiving the oscillator control signal from the AFCcircuit; and a first frequency synthesizer configured to provide clocksignals to at least the first down converter and AFC circuit based uponthe reference frequency signal.
 14. The mobile wireless communicationdevice of claim 13 wherein the GPS receiver includes: a second downconverter configured to down convert received positioning signals; acoherent correlator downstream from the second down converter configuredto correlate locally generated pseudo noise with the receivedpositioning signals; a non-coherent combiner configured tonon-coherently combine correlation results from the coherent correlator;a pseudo-range calculator configured to calculate pseudo-ranges basedupon non-coherently combined correlation results from the non-coherentcombiner; a second frequency synthesizer configured to provide clocksignals to at least the second down converter based upon the referencefrequency signal; and a controller configured to provide control signalsto the coherent correlator and the non-coherent combiner based upon theactivation signal from the AFC circuit.
 15. The mobile wirelesscommunication device of claim 9 wherein the activation signal indicatesthat the oscillator control signal is being varied to provide frequencycontrol of the shared oscillator.
 16. The mobile wireless communicationdevice of claim 9 wherein the shared oscillator comprises a temperaturecompensated and voltage controlled crystal oscillator (TCVCXO).
 17. Amethod of operating a mobile wireless communication device comprising:generating an oscillator control signal and an activation signal with anautomatic frequency control (AFC) circuit of a cellular transceiver;processing received positioning signals with a global positioning system(GPS) receiver; generating a reference frequency signal for the cellulartransceiver and the GPS receiver with a shared oscillator responsive tothe oscillator control signal, the reference frequency signal having anoise contribution thereon due to frequency control of the sharedoscillator based upon the oscillator control signal; and controllingprocessing of the received positioning signals at the GPS receiver basedupon the activation signal from the cellular transceiver to reduce thenoise contribution on the reference frequency signal due to frequencycontrol of the shared oscillator based upon the oscillator controlsignal including controlling coherent correlation of the receivedpositioning signals in a high sensitivity operation mode based upon theactivation signal.
 18. The method of claim 17 further comprisingproviding clock signals to the AFC circuit from a first frequencysynthesizer of the cellular transceiver based upon the referencefrequency signal.
 19. The method of claim 18 wherein processing receivedpositioning signals with the GPS receiver includes: providing clocksignals from a second frequency synthesizer for the GPS receiver basedupon the reference frequency signal; and controlling processing of thereceived positioning signals with a controller of the GPS receiver basedupon the activation signal from the AFC circuit.
 20. The method of claim19 wherein processing received positioning signals with the GPS receiverfurther includes: correlating locally generated pseudo noise with thereceived positioning signals via a coherent correlator; non-coherentlycombining correlation results from the coherent correlator via anon-coherent combiner; and calculating pseudo-ranges with a pseudo-rangecalculator based upon non-coherently combined correlation results fromthe non-coherent combiner; providing control signals to the coherentcorrelator and the non-coherent combiner from the controller based uponthe activation signal from the AFC circuit.
 21. The method of claim 17wherein generating the oscillator control signal and the activationsignal comprises: down converting received communication signals in afirst down converter; generating the oscillator control signal and theactivation signal with the automatic frequency control (AFC) circuit;performing a digital-to-analog conversion of the oscillator controlsignal from the AFC circuit; and providing clock signals to at least thefirst down converter and AFC circuit with a first frequency synthesizerbased upon the reference frequency signal.
 22. The method of claim 21wherein processing received positioning signals with the GPS receiverincludes: down converting received positioning signals with a seconddown converter; correlating locally generated pseudo noise with thereceived positioning signals via a coherent correlator downstream fromthe second down converter; non-coherently combining correlation resultsfrom the coherent correlator with a non-coherent combiner; calculatingpseudo-ranges with a pseudo-range calculator based upon non-coherentlycombined correlation results from the non-coherent combiner; providingclock signals with a second frequency synthesizer to at least the seconddown converter based upon the reference frequency signal; and providingcontrol signals from a controller to the coherent correlator and thenon-coherent combiner based upon the activation signal from the AFCcircuit.
 23. The method of claim 17 wherein the activation signalindicates that the oscillator control signal is being varied to providefrequency control of the shared oscillator.